Marc Morano, a former advisor to U.S. Senator James Inhofe and who now runs the website Climate Depot, said that Tuesday's event would "sow confusion" among Catholics about the teachings of the church. "The Vatican is essentially going to confuse Catholics into thinking that your position [on climate change] ... is now an article of faith, is part of Catholic doctrine," Morano said. Morano and others at the event also cited Francis' concern for those impoverished around the world, saying that policies to fight climate change would limit opportunities for growth in developing countries. "Fossil fuels are the moral choice for the developing world," said Morano, who also quoted what he said were words by Australian Cardinal George Pell on the subject.

Pell has voiced his own skepticism of climate change in the past, most notably in 2011 in a lecture hosted by the Global Warming Policy Foundation, a U.K.-based think tank that has challenged the science of climate change and policies addressing it.